This invention relates to subterranean treatments and, more particularly, in certain embodiments, to methods of stimulating a high-permeability subterranean formation which provide an element of control over fluid leakoff and proppant pack formation.
To increase the production of desirable fluids, subterranean wells (such as hydrocarbon producing wells, water producing wells, and injection wells) may be stimulated by traditional hydraulic-fracturing treatments. In traditional hydraulic-fracturing treatments, a viscous fracturing fluid is pumped into a portion of a subterranean formation at or above a rate and pressure sufficient to create or enhance one or more fractures in the formation. It should be understood that there is growing evidence that stimulation by hydraulic fracturing in unconsolidated or poorly consolidated formations may not produce brittle fractures (macroscopic cracks or fissures), as would be expected in more consolidated formations. Rather, a region of high permeability may form, due, in part, to shear failure near the tip of the would-be fracture. To the extent that the methods disclosed herein are applicable to both brittle fractures and regions of high permeability produced by hydraulic-fracturing treatments, the term “fracture” will be used to generally describe the immediate physical results of hydraulic fracturing stimulation of a subterranean formation.
During traditional hydraulic-fracturing treatments, particulate solids, such as graded sand, may be suspended in a portion of the fracturing fluid and deposited in the fractures. These particulate solids, or “proppant particulates,” serve to prevent the fractures from fully closing once the hydraulic pressure is released. By preventing the fractures from fully closing, the proppant particulates aid in forming channels through which fluids may flow. In some instances, fracturing and gravel-packing treatments may be combined into a single treatment, often referred to as a “frac pac” treatment. In gravel packing treatments, larger particulate solids (commonly referred to as “gravel particulates”) may be suspended in a fluid for delivery to a desired area in a well bore, e.g., near unconsolidated or weakly consolidated formation zones, to form a gravel pack to enhance sand control. One common type of gravel-packing treatment involves placing a sand-control screen in the well bore and packing the annulus between the screen and the well bore with the gravel particulates of a specific size designed to prevent the passage of formation sand. The gravel particulates act, among other things, to prevent the formation particulates from occluding the screen or migrating with the produced hydrocarbons, and the screen acts, among other things, to prevent the particulates from entering the production tubing.
The downhole pressure needed to create or enhance one or more fractures in a subterranean formation is a function of the hydrostatic pressure (e.g., the weight of the hydrostatic column) and the surface pressure, provided by the pumping equipment, less the frictional pressure losses due, in part, to the tubing and other downhole equipment as the fracturing fluid passes therethrough. Due to the volume of fluids and proppant required in typical fracturing and frac pac treatments, supply vessels may be required. However, access to the requisite vessels may not be possible in certain locations, particularly internationally. Conventional gravel packing and cementing equipment may be available at these locations, but the size of the jobs typically precludes use of the gravel packing and cementing equipment.